This invention relates to diving equipment and more particularly to an improved regulator valve for controlling the pressure in a diving helmet forming part of what is known as a push-pull diving system wherein the exhaust gas, rather than being vented to the water, is sucked back to its source for purification, enrichment, and reuse. Such a regulator is essential to the operation of such a system for, if helmet pressure is not properly controlled, the diver can be exposed to dangerous pneumatic effects. If the pressure gets too high, he may be subject to embolism or pneumothorax. If the pressure gets too low, he may be subjected to a "squeeze," and be physically forced into the helmet by hydrostatic pressure. Both conditions must be avoided.
Moreover, it is most important that the diving apparatus assure the diver the capability of free breathing so as to minimize the actual physical work that the diver must do in order to breath. The diver who must gasp for his air will not be capable of functioning efficiently at his job, nor will he be as physically secure as if he were able to breathe more freely. At greater depths, the breathing gas increases in density and resistance to flow, thereby making it important to provide a regulation valve that minimizes excursions in helmet pressure and concomitantly minimizes the effort expended by the diver in breathing.